High temperature-resistant waterproof caseless primer

ABSTRACT

A combustible primer for use with caseless small arms ammunition, the primer being resistant to water, and elevated temperatures and less prone to accidental ignition and cook-off. The primer pellet is completely surrounded by energetic, hightemperature resistant, waterproofing seals, none of which require any liquid binder for room temperature pressure bonding thereof.

United States Patent Quinlan et a1.

HIGH TEMPERATURE-RESISTANT WATERPROOF CASELESS PRIMER Inventors: Joseph B. Quinlan; Earl F. Van Artsdalen, both of Philadelphia, Pa.

Assignee: The United States of America as represented by the Secretary of the Army Filed: June 8, 1971 Appl. No.: 151,087

US. Cl. ..102/45, 102/DIG. 1

Int. Cl ..F42b 3/10 Field of Search ..l02/45, 86.5, DIG. 1, 40, 38

References Cited UNITED STATES PATENTS 8/1967 Quinlan ..102/38 1451 Oct. 17, 1972 3,345,945 10/1967 Quinlan et al. ..lO2/38 3,580,180 5/1971 Gawlick et a1 ..l02/45 3,528,187 9/1970 Harrell ..l02/38 X 3,613,587 10/1971 King ..102/40 Primary Examiner-Robert F. Stahl Attorney-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Arthur M. Suga [5 7] ABSTRACT A combustible primer for use with caseless small arms ammunition, the primer being resistant to water, and elevated temperatures and less prone to accidental ignition and cook-off. The primer pellet is completely surrounded by energetic, high-temperature resistant, waterproofing seals, none of which require any liquid binder for room temperature pressure bonding thereof.

4 Claims, 1 Drawing Figure PAIENTED B I972 3.698.319

\NVENTORS JOSEPH B, QU\NLAN EARL. F. VAN ARTSDALEN r A f ATTORNEYS 1 HIGH TEMPERATURE-RESISTANT WATERPROOF CASELESS PRIMER The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of 5 any royalty thereon.

This invention relates to ammunition, and more particularly concerns environmentally protected combustible primers employed in caseless small caliber ammunition up to about 30mm.

In the past attempts were made to surround primer pellets with a granular propellant during the molding process for achieving desired environmental protection for the primer. ln the main, these attempts to so protect the primer were not successful due to migration of the primer from its desired location during the molding process, and thus resulting in unpredictable functionmg.

Our invention substantially overcomes the deficiencies and infirmities inherent in the prior art by providing completely waterproof and energetic seals about the primer pellet, the entire primer assembly being heat resistant to the extent that cook-off and accidental ignition thereof will no longer pose serious military problems.

Thus, a principal object of the invention is to provide an environmentally protected combustible primer which is completely resistant to water and generally not prone to cook-off and accidental ignition.

Another object of the invention is to provide a primer assembly which requires absolutely no liquid binder in its fabrication, thus permitting rapid pelletization and pressure bonding of respective parts.

These and other objects and advantages of our invention will be apparent upon reference to the description which follows when taken in conjunction with the drawing which shows a sectional view of an embodiment of the invention.

Referring now to the drawing, a primer cup is shown at 10, compression molded from granular high temperature resistant propellant, such, for example, as a mixture of cyclotetramethylene tetranitramine (hereinafter referred to as HMX) and rubber, the latter being present in an amount of about 14 to 18 weight percent. The rubber may suitably be a copolymer of 60 percent butadiene and 40 percent acrylonitrile having an empirical formula of C H N or it may be a styrene butadiene. If desired, a commercial catalyst comprising benzoyl peroxide and tricresyl phosphate may be added to the mixture in an amount of from 0.2 to 0.4 weight percent. The method of preparing the above high temperature propellant forms no part of this invention, one of which is fully described in U. S. Pat. No. 3,269,880, owned by the assignee of this invention.

Other high explosives, such as cyclotrimethylene trinitramine (hereinafter referred to as RDX), or pentaerythritol tetranitrate (hereinafter referred to as PETN) and the like may be used, the range of rubber percentages remaining substantially the same. Or the high temperature propellant may comprise about 82 to 87 weight percent of RDX, HMX or PETN, the balance being nitrocellulose or cellulose nitrate.

No liquid binder is needed in compression molding cup 10, nor any other component of our inventive primer assembly. Being completely devoid of liquid binder, the cups may be rapidly pelletized at room temperature, and the other components of our primer assembly fabricated rapidly and facilely.

The cup 10 is provided with an axial recess 12 which is adapted to receive inner seal 14, made of a waterproof plastic explosive comprising, by weight, about to percent PETN, about 8 to 12 percent nitrocellulose, and about 20 to 25 percent of a suitable elastomer, such as any of those rubber compounds aforedescribed used in making cup 10, which will not include the nitrocellulose or cellulose nitrate propellants. Since the rubber or elastomer compound provides waterproofing properties to the inner seal but is non-energetic, every effort should be made to keep its content to a minimum. Of course, other high explosive compositions may be used advantageously in place of PETN, such as RDX or HMX.

The thickness of inner seal will preferably be 0.003 to 0.005 inches for a 5.5 6mm cartridge.

The primer pellet 16, disposed within the pocket provided by inner seal 14 and cavity recess 12, as shown, will preferably be a modified styphnate mix having the following composition, although not limited thereto:

Lead Styphnate 36% Tetracene l2 Barium Nitrate 22 Lead dioxide 9 Antimony Sulfide 7 Zirconium 9 PETN 5 The pellet will be sensitized with a force of about pounds.

The outer seal 18 will comprise the identical composition and thickness of the inner seal and will be pressure bonded at room temperature to propellant seal 20, both of which will then be pressure bonded at room temperature to propellant to the primed primer cup. It should be noted that cup cavity 12 necessarily provides an annular flanged portion therearound 22, upon which outer portions of inner seal 14 are bonded.

Disc propellant seal 20 will be a suitable high temperature resistant propellant, preferably of the same composition as that comprising cup 10, and should be about 0.010 to 0.015 inches thick for a 5.56mm cartridge. The propellant used for propellant disc seal 20 should have a suitable web size, i.e., a web to perforation ratio of approximately 1, thus assuring ease of fabrication.

For small arms ammunition other than 5 .56mm and up to 30mm those skilled in this art will know the relative thicknesses of components which will operate satisfactorily with our invention.

It is apparent from the foregoing description that we have provided a combustible primer with good environmental protection from water and heat, the primer assembly being fabricated from components requiring absolutely no liquid binder whatsoever.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

We claim:

1. An environmentally protected combustible prim er for caseless small caliber ammunition comprising a molded propellant primer cup having an axial recess disposed therein providing an annular flange portion therearound,

an inner seal bonded to said flanged portion and said recess to form a pocket therein,

a primer pellet disposed within said pocket,

an outer seal bonded against said inner seal and pellet, and

a propellant disc seal bonded over said outer seal,

said seals and cup being energetic and devoid of liquid binder while resistant to accidental ignition, and said inner and outer seals being additionally completely resistant to water.

2. The primer of claim 1 wherein said primer cup and said disc seal comprise a high temperature resistant propellant mixture of a high explosive selected from the group consisting of HMX, RDX and PETN, and the balance being selected from the group consisting of nitrocellulose and cellulose nitrate, said high explosive being present in an amount ranging between about 82 to 87 weight percent of said mixture.

3. The primer of claim 1 wherein said primer cup and said disc seal comprise a high temperature resistant propellant mixture of a high explosive selected from the group consisting of HMX, RDX and PETN, and the balance being selected from the group consisting of styrene butadiene and a copolymer of 60 percent butadiene and 40 percent acrylnitrile having an empirical formula C I-l N said high explosive being present in an amount ranging between about 82 to 86 weight percent of said mixture.

4. The primer of claim 1 wherein said inner and outer seals comprise a high explosive selected from the group consisting of HMX, RDX and PETN, an elastomer selected from the group consisting of styrene butadiene and a copolymer of 60 percent butadiene and 40 percent acrylonitrile having an empirical formula C H gN0.4; and nitrocellulose, said high explosive being present in an amount of about 65 to weight percent, said nitrocellulose being present in an amount of 8 to 12 weight percent and said elastomer being present in an amount of 20 to 25 weight percent. 

1. An environmentally protected combustible primer for caseless small caliber ammunition comprising a molded propellant primer cup having an axial recess disposed therein providing an annular flange portion therearound, an inner seal bonded to said flanged portion and said recess to form a pocket therein, a primer pellet disposed within said pocket, an outer seal bonded against said inner seal and pellet, and a propellant disc seal bonded over said outer seal, said seals and cup being energetic and devoid of liquid binder while resistant to accidental ignition, and said inner and outer seals being additionally coMpletely resistant to water.
 2. The primer of claim 1 wherein said primer cup and said disc seal comprise a high temperature resistant propellant mixture of a high explosive selected from the group consisting of HMX, RDX and PETN, and the balance being selected from the group consisting of nitrocellulose and cellulose nitrate, said high explosive being present in an amount ranging between about 82 to 87 weight percent of said mixture.
 3. The primer of claim 1 wherein said primer cup and said disc seal comprise a high temperature resistant propellant mixture of a high explosive selected from the group consisting of HMX, RDX and PETN, and the balance being selected from the group consisting of styrene butadiene and a copolymer of 60 percent butadiene and 40 percent acrylnitrile having an empirical formula C3.6H4.8N0.4, said high explosive being present in an amount ranging between about 82 to 86 weight percent of said mixture.
 4. The primer of claim 1 wherein said inner and outer seals comprise a high explosive selected from the group consisting of HMX, RDX and PETN, an elastomer selected from the group consisting of styrene butadiene and a copolymer of 60 percent butadiene and 40 percent acrylonitrile having an empirical formula C3.6H4.8N0.4; and nitrocellulose, said high explosive being present in an amount of about 65 to 75 weight percent, said nitrocellulose being present in an amount of 8 to 12 weight percent and said elastomer being present in an amount of 20 to 25 weight percent. 